In some communication systems, such as Time Division Multiple Access (TDMA) systems, wireless communication devices operating in these systems are required to monitor multiple channels for radio frequency (RF) activity. For example, a wireless communication device may monitor channels having different priority levels, wherein the device remains on a lower priority channel a majority of the time and periodically leaves the lower priority channel to inspect a higher priority channel for RF activity of interest. The time that it takes to inspect the higher priority channel and return to the lower priority channel (if no RF activity of interest is present) causes a hole or gap in audio being received on the lower priority channel. The length of that audio hole affects the quality of the audio signal heard by a user of the wireless communication device. Thus, it is desirable to shorten the duration of the channel inspection on the higher priority channel to a minimum amount of time in order to maximize the audio quality of an RF signal on the lower priority channel.
One method used for minimizing the duration of an audio hole is called channel marking, which uses the results from one channel inspection to make assumptions about what to expect during the next channel inspection of the same channel. During the channel marking process, if a channel is not marked, a full inspection is performed to validate whether or not RF activity on the channel is of interest. If the activity is not of interest, the channel is “marked” to cause the communication device to perform only a partial channel inspection upon next returning to the channel. The partial inspection is of a shorter duration, which thereby shortens the duration of the audio hole associated with the partial inspection. Although some current channel marking schemes exist, they generally cause audio holes from both the full inspection as well as one or more partial inspections. In addition, none of them are optimized for the situation of when the radio is monitoring one or more slots of an RF channel and periodically performing channel inspections on another slot of the same RF channel looking for RF activity of interest.
Thus, there exists a need for a method for performing channel inspections that can eliminate partial inspections in many instances.
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